Chlorofluorocarbons (CFC's) are widely used in refrigerant compositions, propellants and cooling fluids as well as blowing agents, solvents and rinse agents. Their replacement with environmentally acceptable alternatives has produced an abundance of compounds meeting one or more of these needs. The most acceptable replacement compounds are those having little or no chlorine, since it is generally accepted that chlorinated aliphatics lead to unacceptable reactive chlorine-containing radicals when present in the upper atmosphere. These radicals are thought to react with the ozone in the stratosphere depleting it to dangerously low levels.
One of the more promising alternatives to CFC's are aliphatic compounds where chlorine has been replaced with fluorine. These materials are known as hydrofluorocarbons (HFC's). Typical HFC's have atmospheric lifetimes and global warming potentials that are a fraction of their chlorinated analogs. Fortunately, many of their other physical properties (low flammability and toxicity, sufficient volatility, etc.) are identical or similar to the CFC's. Accordingly, they are attractive replacements for the chlorinated molecules.
In processes for preparing HFC's, a usual starting material is the chlorinated analog of the desired fully fluorinated compound. Thus, U.S. Pat. No. 2,787,646 discloses that SbF.sub.3 Cl.sub.2 and.backslash.or SbF.sub.3 are useful for converting compounds of the formula CMZ.sub.2 CX.dbd.CHY, for example 3,3,3-trichloroprop-1-ene or 1,1,3-trichloroprop-1-ene to compounds of the formula CF.sub.3 CX.dbd.CHY, for example 3,3,3-trifluoroprop-1-ene.
U.S. Pat. No. 2,549,580 discloses the conversion of 1,1-dichloroprop-1-ene to 1,1,1-trifluoropropane by means of HF at 120.degree. C. and 800 psi pressure.
U.S. Pat. No. 5,616,819 discloses a two step process for the preparation of fully fluorinated aliphatic hydrocarbons in which hydrogen fluoride is reacted with a chlorofluoro olefin in the presence of a catalyst for a time and at a temperature sufficient to form said fully fluorinated aliphatic hydrocarbon.
The preparation of 1-chloro-1,1,3,3,3-pentafluoropropane and of 1,1,1,3,3,3-hexafluoropropane from 1,1,1,3,3,3-hexachloropropane in the liquid phase is described in EPO Publication No. 0 522 639 A1. While the preferred catalyst for the reaction is noted to be SbCl.sub.5, other catalysts disclosed are those metal chlorides, fluorides, and chloride fluorides of Group IIIa, IVa, IVb, Va, Vb and VIb of The Periodic Table of the Elements.
Compounds such as 1,1,1,3,3,3-hexafluoropropane are prepared by the coupling of two chlorine containing reactants, i.e., 1,1,1-trichloro-2,2,2-trifluoroethane and dichlorodifluoromethane, in the presence of hydrogen and a first catalyst to form an olefin, i.e., 1,1,1,3,3-pentafluoro-2-chloroprop-2-ene and then hydrogenating the olefin in the presence of a second catalyst. See WO 95/05353.